The role of natural language in a multimodal interface

Although graphics and direct manipulation are effective interface technologies for some classes of problems, they are limited in many ways. In particular, they provide little support for identifying objects not on the screen, for specifying temporal relations, for identifying and operating on large sets and subsets of entities, and for using the context of interaction. On the other hand, these are precisely strengths of natural language. This paper presents an interface that blends natural language processing and direct manipulation technologies, using each for their characteristic advantages. Specifically, the paper shows how to use natural language to describe objects and temporal relations, and how to use direct manipulation for overcoming hard natural language problems involving the establishment and use of context and pronominal reference. This work has been implemented in SRI's Shoptalk system, a prototype information and decision-support system for manufacturing.